438 



STATE BOARD OF AGRICULTURE. 



At 17 days the Stock lactic check and the cultures growing in the 

 milk containing heated filtrate contained a slight amount of soft curd, 

 perhaps 2 mm. deep in the bottom of the flask. 



At this same time the lactic bacteria in the cultures containing 5 cc. 

 and 25 cc. of the heated and unheated filtrate are rapidly on the de- 

 crease. This might be attributed to deleterious substances other than 

 acid, formed by the lactic bacteria from certain principles of the fil- 

 trate, but a more plausible explanation seems to be that certain con- 

 stituents of the filtrate stiniulMte the organisms to jtrodiice an abnor- 

 mally large amount of acid, the excess of which is sullicicnt to cause a 

 rapid reduction of their numbers. Ordinarily the maximum acidity pro- 

 duced by the Stock lactic in milk culture is about +40°, consequently 

 the acidity of +70° to +90° is sufficient to effect its destruction in a 

 short time. 



In Tables XVI, XVII and XIX the disappearance of the lactic or- 

 ganisms cannot be attributed alone to the amount of acid present, as 

 the difference in acidities between the check cultures and those con- 

 taining the filtrate is but slight, not enough to cause the marked 

 diminution in numbers which occurred. 



Expt. IV. 



Determination of the Mechanism of the Enz3-mic Action. 



The next question arising was whether this stimulating power of the 

 filtrate was due to enzjmic action upon the cell itself or upon the milk 

 constituents by means of which they would be changed into a more 

 available form for Aveak lactic bacteria. An endeavor to solve this ques- 

 tion was made in the following way : 25 cc. of sterile unheated filtrate 

 was introduced in each of 2 flasks containing 250 cc. each of sterile milk 

 and left 48 hrs. at room temperature (see Table XX; 25 cc. unheated 

 filtrate). One flask was then heated in flowing steam for 5 minutes and 

 cooled; both flasks were then inoculated with 1 cc. of a milk culture 

 of Stock lactic, titrated and plated every day or so. The milk contain- 

 ing the filtrate, u])on being heated, curded with a marked extrusion of 

 whey, the curd Avas v<'ry tough and hard to break up by shaking. This 

 fact may account for the low initial count in this flask; both flasks 

 should have had directly comparable initial counts as both the amount 

 of milk in the flask and the inoculum were the same in each. These 

 data are tabulated in Table XXI: 



